STUDIES OX THE ECTOPAKASITTC TREMATODKS OF JAPAN. m 



suppose the cells to shrink soon after discharging their contents. In 

 these goblet-shaped cells just mentioned I could observe a distinct 

 cell -membrane. In the immediate neighbourhood of these cells there 

 are in Monocotyle numerous large cells of an irregular shape, each with 

 a I'ather small nucleus which contains a single nucleolus, and with 

 a coarsely granular, well-staining protoplasm destitute of an external 

 membrane. Judging from their similarity to the shell-glands of 

 other genera and from the fewness of the goblet-shaped cells above 

 mentioned in the genus under question, I think they are shell-glands 

 which are still in the interval in secretory activity. 



As stated above, the ootyp is characterised by the fact that it 

 receives the openings of the shell-glands. It is, moreover, separated 

 from the oviduct by a constriction, which is usually very distinct — 

 " vine sorte de pylore " as P. J. v. Beneden'^ calls it. Anteriorly 

 it is in most species directly continued into the uterus without 

 undergoing any constriction ; but in many species of Tristomum (T. 

 simiatwn, T. ovale, T. hijMrasiticwn, and T. foliaceuni) its anterior 

 extremity protrudes into the hinder end of the uterus, just in the 

 same way as the neck of the uterus projects into the vagina in the 

 mammalia ; so that in this genus the uterus and the ootyp may be 

 said to be separated from each other by a valve, which allows a body 

 to pass from the latter into the former but not in the contrary direc- 

 tion (PL XXII, fig. 3). In Monocotyle the ootyp opens directly into 

 the genital atrium, the uterus being totally wanting in this genus. In 

 Axine, Microcotyle, Octocotyle, Diclidophora, and Hexacotyle the wall of 

 the ootyp is not specially different from that of the oviduct; i. e., it con- 

 sists of a thin, homogeneous, protoplasmic layer resting on a basement 

 membrane ; but in some species there is an assemblage of oval nuclei 

 at the entrance of the oviduct (PL IV, fig. 4). In some cases there 



1). p. J. T. Beneclen — Memoire sur les vers intestinaux. p. 43. 



